Using a VMA on more than one timeline concurrently is the exception
rather than the rule (using it concurrently on multiple engines). As we
expect to only use one active tracker, store the most recently used
tracker inside the i915_vma itself and only fallback to the rbtree if
we need a second or more concurrent active trackers.
v2: Comments on how we overwrite any existing last_active cache.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_vma.c | 50 +++++++++++++++++++++++++++++++--
drivers/gpu/drm/i915/i915_vma.h | 1 +
2 files changed, 49 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index cd94ffc7f079..33925e00f7e8 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -119,6 +119,12 @@ i915_vma_retire(struct i915_gem_active *base, struct i915_request *rq)
__i915_vma_retire(active->vma, rq);
}
+static void
+i915_vma_last_retire(struct i915_gem_active *base, struct i915_request *rq)
+{
+ __i915_vma_retire(container_of(base, struct i915_vma, last_active), rq);
+}
+
static struct i915_vma *
vma_create(struct drm_i915_gem_object *obj,
struct i915_address_space *vm,
@@ -136,6 +142,7 @@ vma_create(struct drm_i915_gem_object *obj,
vma->active = RB_ROOT;
+ init_request_active(&vma->last_active, i915_vma_last_retire);
init_request_active(&vma->last_fence, NULL);
vma->vm = vm;
vma->ops = &vm->vma_ops;
@@ -895,6 +902,22 @@ static struct i915_gem_active *lookup_active(struct i915_vma *vma, u64 idx)
{
struct i915_vma_active *active;
struct rb_node **p, *parent;
+ struct i915_request *old;
+
+ /*
+ * We track the most recently used timeline to skip a rbtree search
+ * for the common case, under typical loads we never need the rbtree
+ * at all. We can reuse the last_active slot if it is empty, that is
+ * after the previous activity has been retired, or if the active
+ * matches the current timeline.
+ */
+ old = i915_gem_active_raw(&vma->last_active,
+ &vma->vm->i915->drm.struct_mutex);
+ if (!old || old->fence.context == idx)
+ goto out;
